Vehicular traffic at intersecting streets is typically controlled by traffic control lights. These lights include the well-known red, yellow and green lights as well as lights to indicate protected turns. Typically the lights are operated in accordance with predetermined timing sequences by a controller. Various controllers have been developed and used to control traffic lights. The controllers in use include electromechanical controllers of various types, electronic controllers, and controllers which include microprocessors to generate various timing and control signals. One disadvantage with such traffic signal controllers is that to change the operation of the traffic lights at an intersection, an individual would typically be required to travel to the intersection and enter permanent or temporary changes into the controller. Changes in the operation of the controller may be desirable to modify the timing of the lights or the sequence of operation. Such changes may be necessary as a result of changed traffic patterns, special events, construction or for numerous other reasons.
There are traffic control systems in which centralized computers control local controllers. A significant disadvantage to centralized control systems is that each local traffic signal controller is physically located near the traffic signals to be controlled and the centralized control arrangement must communicate with the traffic signal controllers either over a hard wired network or by means of specialized radio equipment. The expense of providing centralized control of traffic control signals over a large number of intersections is often prohibitive.
The problem of traffic management under varying conditions is a significant problem and one for which an inexpensive solution is desired.